1. Field of the Invention
This invention relates to trains for carrying railroad rails, and in particular trains for carrying long lengths of ribbon rail.
2. Description of the Related Art
Modern railroad tracks are constructed using long sections of ribbon rail which presently may be up to 1600 feet in length. These sections of ribbon rail are formed by butt welding multiple sticks of rail, which traditionally come from the steel mill in thirty-nine foot or seventy-eight foot lengths. The welding of the ribbon rails is done at a welding plant and the welded ribbon rails are transported to their installation site on a specially constructed rail train. When existing track is being replaced, ribbon rails may be unloaded from the rail train using a rail unloading machine, such as the Rail unloading machines disclosed in U.S. Pat. No. 6,981,452 and U.S. Patent Application Publication No. 2008/0141893, both to Herzog et al. The rail unloading machine pulls one or two rails off of the rail train as the rail train moves down the existing track and lays it alongside the existing rails.
Prior art rail trains traditionally comprise of a plurality of 60 foot flatcars connected together by standard railroad couplers. Each car includes a pair of transverse stands for supporting the ribbon rail. The stands of each car are spaced 30 feet apart and 15 feet from the respective coupler such that the stands are spaced 30 feet apart along the length of the rail train. The stands each include multiple tiers (typically five or six tiers) which each support a plurality of rails (for example eight to twelve rails per tier). The stands must each be strong enough both to support the weight of the rails and to resist side loads created by flexing of the ribbon rails as the rail train traverses curves in the track. Thirty foot spacing for the stands is believed to be optimal for supporting the rails without excessive sagging.
One car in each rail train is a tie-down car including a specialized stand which includes means for fixing the rails to the racks to prevent longitudinal movement of the rails relative to the tie-down car. The fixing means generally includes a plurality of clamping blocks which are bolted to the stand on opposite sides of each rail so as to bear against the foot or base flange of the rail and clamp it against the stand. Typically each clamping block is held down by three or four large bolts which must be installed or removed using an impact wrench or the like. All the other racks in the train allow for relative longitudinal movement of the rails and may include rollers which support the rails. This relative movement between the racks and the rails is required in order to allow the rails to flex without stretching or compressing as the train traverses curves in the track, as well as to allow for coupler slack that exists in each of the couplers between cars. Each coupler has up to approximately 6 inches of slack. Coupler slack and thermal expansion and contraction of the ribbon rail, generally necessitates that the tie-down car be positioned near the center of the rail train so as to evenly divide the rails and to thereby insure that neither the forward end nor the rearward end of the rail can move, expand or contract a sufficient distance relative to the nearest adjacent rack that the end of the rail falls off of the rack.
An end car, through which rails are loaded and unloaded, is positioned at the rearward end of the rail train. To unload rails from the rail train a rail unloading machine is coupled to the end car and pulls the rails from the end car. The end car includes a single stand or tunnel to support the ends of the rails and a barrier door rearward of the stand which swings inwardly across the car and acts as a stop to prevent the rails from sliding rearwardly off the rail train should one or more rails come loose from the tie-down car. End cars also typically include a ramp which is pivotally mounted to the deck of the end car rearward of the swing door. The ramp includes a roller on its distal end. The distal end of the ramp can be raised or lowered relative to the deck of the end car and is used to guide the rails upwardly or downwardly as they are being unloaded. An end car with barrier doors may also be located at the front end of the rail train to prevent the rails from sliding forwardly off the rail train should one or more rails come loose from the tie-down car.
A basic problem with existing rail trains is that the design of the cars does not allow the rails to flex evenly as the train traverses a curve. Having two stands per car isolates the portion of the rails located between the stands and holds it in a rigid orientation. Flexion of the rails is then concentrated into the sections located over the couplers. This uneven flexion of the rails causes increased side loads on the stands, as well as stress on the trucks and couplers. What is needed is an improved rail train which preserves optimal spacing of the stands but which allows for uniform flexing of the rails.
Worker safety is further endangered by the need to manually clamp and unclamp the rails using an impact wrench or the like. A clamping mechanism that could be remotely operated would greatly improve the safety of rail loading and unloading operations.
A further problem with prior art rail trains is the limited usefulness of the end car ramp for maneuvering rail. The ramp can support the rail during unloading and can raise and lower the rail within a limited range, but it cannot maneuver the rail inwardly or outwardly. Furthermore, the ramp cannot support a rail in an upright position during unloading and there is a danger of the rail tipping over. Most manipulation of the rail, including all inward and outward movement of the rail, must be performed by the rail unloading machine. The rail unloading machine includes feed boxes for pulling the rail and a crane for grasping and manipulating the rail into the feed boxes. Unloading of rail would be greatly simplified if the end car included improved means for manipulating the rail which could assist with feeding the ends of the rail into the feed boxes on the rail unloading machine.